574 ELEMENTS OF PLANT HISTOLOGY AND MICROTECHNIC 



of ammonio-magnesium phosphate the crystals of which are frequently formed in 

 x- and *-shaped clusters. 



Phycoerythrin. The red coloring matter in the Florideae or red algae. It is 

 soluble in fresh water, leaving chlorophyll behind in the plastids, while in ether 

 the chlorophyll is extracted and the phycoerythin is left. 



Phycocyanin. The blue coloring matter in the blue-green algae. It is soluble 

 in cold water, glycerine and alkalies, giving a blue solution with red fluorescence. 

 It is insoluble in alcohol and ether. 



Phycophsein. The brown coloring matter of the brown algae. It is soluble 

 in fresh water and more readily in hot water, leaving chlorophyll and carotin be- 

 hind in the plastids. It is insoluble in strong alcohol, ether, etc. 



Pipeline, CnH^NOs. Piperine is an alkaloid occurring in the fruit of the Piper- 

 aceae. Very thin sections may be rubbed out somewhat under a cover-glass to 

 press out the ethereal oil, which will then evaporate and leave the piperine to 

 crystallize in the form of minute short needles. A section becomes of a deep red 

 color when treated with concentrated sulphuric acid, while with nitric acid an 

 orange color is produced. When sections are moistened with sodium molybdate, 

 and then treated with concentrated sulphuric acid, they take on a blue color. 

 Piperine is easily soluble in acetic acid. 



Proteids (Albuminoid Substances). Proteids are stained from yellow to brown 

 by a dark solution of potassium iodide-iodine. The dilute solution of iodine recom- 

 mended for starch should not be used, for proteids are stained less readily than 

 starch. Millon's reagent (see under this head in the preceding chapter) colors 

 proteids a brick-red color. If the solution is old and has lost its efficiency, a few 

 drops of a solution of potassium nitrate will probably restore it. Concentrated 

 nitric acid colors proteids yellow, and the addition of ammonium produces a still 

 deeper yellow. When sections lie for an hour or two in a solution of I Gm. of so- 

 dium phospho-molybdate in 90 Gm. of distilled water and 5 Gm. of nitric acid, 

 which has been filtered after standing for several days, the proteid substances 

 appear in the form of yellowish granules. A concentrated solution of nickel sul- 

 phate colors proteid granules yellow or blue. When rather thin sections are placed 

 in a concentrated solution of copper sulphate for about half an hour, and then are 

 placed in water for about an hour, and then are transferred to a concentrated 

 solution of potassium hydrate, proteids are colored red or violet, which becomes 

 deeper when the solution in which the sections are lying is heated somewhat. The 

 pepsin-glycerine and pancreatin-glycerine ferments prepared by Dr. G. Grubler 

 in Leipzig are solvents of proteids. Sections are treated for an hour at a tempera- 

 ture of 4O C C. with a mixture of I part of pepsin-glycerine and 3 parts of water, to 

 which is added 0.2 per cent, of chemically pure hydrochloric acid. Pancreatin- 

 glycerine is employed in the same manner as the pepsin-glycerine. 



Protein Crystalloids. Under Aleurone in the preceding chapter are given 

 methods of differentiating crystalloids in aleurone grains. Protein crystalloids 

 also occur in the cytoplasm, nucleus, and chromatophores, and in all of these cases 

 the crystalloids have essentially the same nature, but they may vary considerably 

 in form. For staining crystalloids, see in the preceding chapter under Acid Fuchsin. 



Protoplasm. The protoplasm of the cell can be studied to advantage by means 

 of the microscope only after being killed and fixed by fixative reagents, q.v. The 

 different constituents of the protoplasm can then be differentiated by means of 

 stains or by means of digestive ferments, such as pepsin and pancreatin. Iron 

 haematoxylin, or a combination of fuchsin and iodine green, or of safranin, gentian 

 violet, and orange G, as recommended under Double Staining in the preceding 

 chapter, are specially to be recommended for differentiating the different parts of 

 the protoplasm. For staining the leucoplasts and chromatophores in general, see 

 Fuchsin, Acid. 



